A newborn is found to have strong, bounding pulses in both upper extremities and carotids

USMLE Question Break Down Biochemistry

Welcome back to MedSmarter’s USMLE Style Question of the Week.  Here’s the breakdown of another high-yield Biochemistry question for those preparing for your USMLE Step 1 or just to gain some knowledge.  As always you want to begin by reading the last sentence of the vignette first to get an understanding of what the question is asking for.

Question Break Down of the Week:

A newborn is found to have strong, bounding pulses in both upper extremities and carotids, but her femoral pulses are very weak. She is diagnosed with coarctation of the aorta and is taken to surgery to correct the defect. Subsequent follow-up examinations show no further heart abnormalities. Fifteen years later, the patient is noted to have poorly developed secondary sexual characteristics, including persistent, non-progressive Tanner stage 2 breast and pubic hair development. She has not experienced menarche. Which of the following would most likely be found in this patient?

(A) Normal ovaries
(B) Decreased estrogen levels
(C) 46.XY karyotype
(D) Simian crease
(E) Patent ductus arteriosus

The correct answer choice is B. The patient in the vignette has a history of coarctation of the aorta at birth and subsequently, at the age of 15, has poorly developed secondary sexual characteristics. These characteristics include persistent non-progressive Tanner stage 2 breast and pubic hair development and no menarche. These findings are consistent with Turner syndrome, which is a condition in which females have only one X chromosome (45 XO). Patients with Turner syndrome have a rudimentary ovary, which leads to decreased estrogen levels, and consequently, delayed or absent puberty. Therefore, the most likely finding in this patient is decreased estrogen levels, which explains her lack of progression through puberty and lack of menarche. The other answer choices are incorrect because they are not consistent with the clinical findings of Turner syndrome.

Did you think the answer was different?

Did you think that the correct answer choice was other than B?  You can view this video for a deeper discussion of why A, C, D, and  E are not the correct answer choices.

Learn to correctly answer basic science knowledge questions and prepare to take your USMLE Step 1 exam.  The MedSmarter roadmap will make your journey to becoming a practicing physician in the United States as painless as possible.

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